So-called self-emulsifying emulsion bases for the production of oil-in-water emulsions contain emulsifiers, oil components and waxes in quantities adapted to one another. The products in question are normally water-free products with a wax-like to solid consistency of which the melting points/melting ranges depend, inter alia, upon the waxes and oil components used, but which generally have melting points of at least 30° C. By using systems such as these, cosmetic chemists save themselves time-consuming tests in the development of cosmetic emulsions. At the same time, the customer enjoys lower costs for warehousing and raw materials testing. Self-emulsifying bases based on fatty alcohols and alkyl oligoglycosides are disclosed, for example, in EP 553 241 A1 and WO 97/18033. Typical self-emulsifying bases are obtainable from Cognis under the names of Emulgade® CL and Emulgade® CBN. To produce emulsions, 10 to 20 parts of these concentrates (self-emulsifying bases) are generally heated, if desired together with other oil components, to a temperature 20° C. above the melting temperature of the self-emulsifying bases and emulsified with 80 parts water also heated to that temperature, optionally followed by the addition of other auxiliaries, such as preservatives, perfume or active components. Emulsions usually having a droplet diameter of ≧10 μm are formed in this way. In order to avoid sedimentation, experience has shown that the viscosity of such emulsions should be >5,000 mPa·s (Brookfield RVF, spindle 5, 10 r.p.m at 23° C.). The scope of application of such concentrates is clearly limited. They are not suitable where processing in an energy-saving cold process is envisaged or where low-viscosity emulsions with a viscosity of ≦1,000 mPa·s are to be developed for use as roll-ons, sprays or as impregnating liquids for wet wipes.
Besides so-called self-emulsifying bases, emulsion concentrates are also commercially available which likewise contain the key constituents of an emulsion, namely emulsifiers, oil components and waxes, and which have a water content of about 60%. These concentrates are typically produced by the PIT process and, accordingly, have a mean droplet diameter of <1 μm and often between 100 nm and 500 nm. They may readily be diluted with cold water and are particularly suitable for the production of roll-on concepts, sprays or as an impregnating liquid for wipes. In combination with viscosity-generating polymers, lotions and creams can also be produced. The disadvantage is that other oil components can only be added with intensive homogenization. In addition, such emulsion concentrates are microbiologically susceptible and cannot be economically transported on account of their high water content. In addition, the PIT concentrates in question can normally only be produced on the basis of ethoxylated emulsifiers. Unfortunately, this class of emulsifiers is being increasingly discussed in negative terms for dermatological and ecological reasons. So-called “ethoxylate-free” nanoemulsions, albeit with a relatively high water content, are known from DE 103 46 515 while ethoxylate-free self-emulsifying bases are known from DE 103 47 940. O/W emulsions with a low water content, i.e. basically concentrates, are known from WO 02/056841. However, these emulsions, which have a water content of at most 30%, can have the disadvantage that they are not stable in storage at >30° C. and also cannot be emulsified with other oil components without relatively high energy consumption.
Accordingly, the problem addressed by the present invention was to provide self-emulsifying emulsion bases or concentrates which would be liquid and hence cold-processable, would have a low water content, could readily be emulsified with other oil components and could be further diluted with water without any separation occurring. Ideally, such concentrates would be present as transparent solutions because, in contrast to conventional liquid emulsion concentrates, systems such as these would have improved long-term stability.